This invention is directed to a seamable chlorosulfonated polyethylene sheet and a process for its preparation.
Sheets of chlorosulfonated polyethylene have been used successfully for roofing and pond and pit liners. The calendered sheets of uncured chlorosulfonated polyethylene are laid side-by-side and overlap at the edges of each sheet where they are to be seamed together by conventional means, for example, hot air welding or adhesive seaming. However, when sheets of uncured chlorosulfonated polyethylene have been exposed to sunlight for a short time, for example, two or three days when stored out of doors at a job site, the seam adhesion of the chlorosulfonated polyethylene sheets is adversely affected and, in many cases, it can no longer be seamed together. For example, when sheets that have been exposed to sunlight for eight hours are heat welded, a secure weld does not develop, and one does not obtain weatherproof bonding of the sheets that is essential when constructing pond or pit liners or when the sheets are used for roofing. Up to the time of the present invention, the uncured chlorosulfonated polyethylene sheets were covered with black polyethylene film so that they could be welded together. This procedure is both expensive and inconvenient.